Telegraphy.



M. I. PUPIN.

TELEGRAPHY.

PATENTED MAY 29, 1906.

' APPLIUATION FILED JAN. 28. 1895.

mzesses a a? U afwwzkdw/A UNITED STATES PATENT or nony. MICHAEL i. ruPIN; or 11551 YORK, N. Y..

' TELEGRAPHY.

- Specification of Letters Patent;

Patented. May 29,1906.

Application and January 28,1895. sms No. scares.

To all whom it may concern:

Be it known that 1, MICHAEL I. Form, of the city, county, and' State of New York, have invented a new and useful Improvement in Telegraphy, of which the following is a specification.

The physical fact upon WlllGlh my inventi n is based is as follows: When a certain number of simple harmonic electromotiv'e ro forces are impressed upon a line conductor,

then a branch line may be adjusted so that it will offer a very much smaller impedanceto one of these electromotive forces than to the others. This will take place when the nat- I 5 ural period of this branch is the same as that of the selected electromotive force. This ph sical fact, is known under the name of e ectrical resonance. To produce electrical resonance between a circuit and an im:

pressed electromotive force, the electromagnetic constants of the line-that is, its selfinduction and electrostatic capacityInust be adjusted according to well-known rules. A resonating line is selective. The possibility of attaching to a main line a certain number of selective branches enables the foregoing princi le to be applied to multiplex telegra'phy. difiiculties appear. "These are, first, that 0 the selective power of an electrically-tuned branch. circuit forming part of a system diminishes materially with the increase in the number of branches from the mam conductor, and, second, that when there are several 3 5 complex harmonic electromotive forces 'im pressed upon the system the upper harmonics of one may come Within the frequencies of the fundamentals of the others, especially if more than three or four frequencies be em 40 ployed, with consequent confusion.

I have here shownmy present invention embodied in a system of multiplex telegraphy; but it is to be understood that'it may e practically employedin various ways and by other forms of apparatus than are' here set-forth, and that hence I do not limit my self to its specific application to multiplex telegraphy. .7 a

My invention consists, first, in the method of and apparatus for throwing upon a main line a'number of alternating currents of dif,

ferent frequencies independently of each other and distributing the energy of these several currents each selectively to a separate electrical translating device; second, in an electrical system wherem one or more induced .penden'tly of one another and'of all n practice, however, certain serious.

circuitsmay be tuned in electrical resonance respectively .with the impressed electromotive forces of different periodicities and this indethe rest of the system to which they belong; third, in

- the method and apparatus for converting a complex harmonic electromotite force 1m-.

pressed upon an electrical system into a simple harmonic electrolnotive force; fourth, in the construction and arrangement of the multiplex telegraph, hereinafter described.

The accompanying drawings are'an electrical diagram. I 1

Figure 1 illustrates a multiplex telegraph line not provided with the tuned induced cir-.,

cuits hereinafter described. Fig. 2 illustrates a multiplex telegraph-line embodying my present invention.

S1 mil ar characters of reference indicate like properly adjusting the self-induction A and the capacity B in each branch they can be made selective with respect to the four im-' pressed electromotive forces; but it will be found that their selective power, even under most favorable conditions, will be toosmall for practical purposes, especially whenthe static capacity and the self-induction of, the

' line 2 itself are considerableas, for instance,

in the case of long telegraph-lin'es' This is evident from purely theoretical reasons alone, while experimental investigations have convinced me that it is practically impossible to obtain-a satisfactory balance in a system of this description, since the variation in the electrical constants in any one of the branches or in the main line will effect seriously, the resonance balance in every other branch; By making, however, each of the sialf-induc tions A of the several branches very large in comparison with the self in'duction' of the line tolerably satisfactory results can be obtained. This remedy of the difficulty is evidently not applicable in thecase of long telegraph-lines, since in these the self-induction and static capacity are too large. In. such event the best. that can be done is. to establish by adjustments as described an approxi mate resonance in the various branches.

Referring now tol ig. 2, 7, 8, 9, and 10 are altema'tingwurrent generators giving four electromoti-veyforces of four different frequencies. These' generators are. connected j gqzto the primary circuits of four transformers '1 simultaneously orotherwise.

11 12 1314, independently of each other and The secondary circuits of these transformers form part of the main line 2.. The cores'of the transformers are of finely-laminated iron and form closed or'very nearly closed magnetic circuits. vI

. wi h to emphasize this fact because it is one Connecte of the-im ortant features of my invention. to the. main line 2 and to "the ground .G' are four branches 3 4 5 6. 7 Each one of these branches, as 3, has a primary coil and another coil or coils A. The coil 0, I shall call the active coil iand the coil A theauxiliary coil; Also in each branch is a condenser or conden'sersB. The number of auxiliary coils and condensers in each branch may be any number, all of them connected in series. 'Each branch is placed by means of T the active coil in inductive relation to a seconda circuit. Thus, for instance, the

branc 3'is in inductive relationto the circuit 15, which includes a coil D of large and adjustable selfinduction a condenser E of Suitable capacity for telegraphic purposes, and any suitable apparatus H which serves to indicate a current in this circuit by means 'of an electromagnetic, electrochemical, or electrostatic effect.

Four keys F serve the. purpose of making and breaking or simply varying the. strength of the generator-current.

The four generators 7 8 9 10, with the transformers 11 12 13 14 and the keys F, consti- U tute the outfitfor the four sending-stations;

The four branches 3 4 6, with their four secondary circuits, constitute four distinct receiving-stations,

The-method of'o erating is as follows: Let I the frequencies of t egenerators at the sending-gstations' be, respectively, six hundred,

Ifive'hundred and twenty,-four hundred and,

: forty, and three-hundred and sixty-periods per second. The branches 34 5 6 being atthe receiving-stations are adjusted by means of the condensers B and the auxlhary 0011s .of each other.

A, so as'to. be approximately in resonance withthe frequencies aforesaid, respectively.

These branches are adjustable independently The secondary circuits 15 1'6 17 18 i'neach re'ceivin -station are put" in perlarge a self-induction that the self-induction b or current.

of each secondary circuit is practically equal to the self-induction of its auxiliary coil, The capacities'are the adjusted according to the well-known rules inorder to roduce resonance with the frequency at which each receiving-station is intended to Work. By

keeping down the resistance of the-secondary circuits and by avoiding the use of iron in the auxiliary coils of these circuit s they. can be made easily to respond a thousand times more strongly to the frequency to which they are tuned than to any other frequency, and

this independently of whatever varlations in the electrical constants may be going'on in .the other arts of thesystem. Supposing now that t e four generators at the sendingstations impress simple'harmonic forces upon theline and that the primary circuits are.

closed, there .will be electromotive force'sof the above frequencies impressed on the lin and hence alternating currents of like frequencies, respectively, on the secondary circuits at the receiving-stations. If the pri. -mary current from, say, generator 7 is inter rupted, then the current in the corresponding branch -say 3w'ill also be interrupted,

whereas the currents in the other branches at the other receivingstations will not be .affected. Hence if an operator works a key,

as F, the sounder H in the secondary circuit 15 will be operated, but not the'soundersin. any of the other secondary circuits.

It is evident that any number of transmitting and receiving-stations can be working simultaneously on the same line without dis turbin each other. The limit tothis number wil be determined by the limiting frequencies at which the lines can Work. On a line, say, five hundred miles long, the hi hest fre uency will robably be six hundre perio s per second and the lowest forty. An frequency employed should'be at leas teen per cent. of its own value distant from the next higher and the next lower frequency, so that a line five hundred miles long could be worked conveniently-at from twelve to sixteen different frequencies, and therefore have ,twelve to sixteen transmitting and receiving stations. This is, however, on the supposition that each transmitting-station sends asim'ple harmonic electromotlve force It is, however, practically impossible to produce alternating-current generators capable of giving such a force. As a IIO rule they give alternating electromotive forces inwhich the u per harmonics, especially the third and tile fifth, are of nearly the same order of magnitude as the fundamental. Hence although the fundamental frequency of any one of the sending-stations does not come within the proximity of the core forms an ordinary closed ma netic circuit quency is equal to thefundamental frequency of the impressed electromotive force, no matter how complex the impressed electromotive force may be. This is especially true if the fundamental frequency five periods per second, and if ma netic lea age is encouraged by arranging t e primary and the secondary circuitin such a way as that they do not overlap, somewhat in the fashion of constant-current transformers em: Ioyed for alternating-current arc lighting.

t is such-transformers that I prefer toem- V ploy in my present system of multiplex telegraphy. I

It will be seen in each oftheforms shown that 'I have a system of interrelated conductors, including parts, whether they be branches or se arate circuits, containing selfdesired frequency. The selectivity of the of a main l1ne, means for throwing several induction 00' s and condensers by which these parts can be made selective each'to a system lies in these selective parts.

I claimv p 1. In an electrical system the combination electromotive forces of different frequencies onto the main line through transformers having cores which form closed magnetic circuits and having large magnetic leakage,selective parts connected to the main line, and means for tuning each selective part to respond to one of the electromotive forces thrown upon the main line, substantially as described.

2. The combination in a telegraphic system containing two or more circuits of means for imposing upon said system electromotive forces of predetermined periodicities, means for electrically tuning each of said circuits to an approximate resonance with one of said electromotive forces, by properly proportioning' its electromagnetic constants with re-' a circu1t 1n inductive re-.

spect to the system, lation with each of said-tuned circuits tuned to a complete resonance with one of said peently of the rest of the system, substantially as described. p

. The combination in a telegraphic system of twoor more circuits and a means'of imposing upon said system an electromotive force of previously-selected periodicity and for electrically tuning it to approximate resonance Withsaid.

in one of said circuits means electromotive force (by properly proportioning its electrical constants with respect to the is not below thirty- 1 r1odic electromotive forces and independ- .'rest of the system) a circuit in inductive relation to said tuned circuit including a self-induction coil and a capacity; the said coil being so proportioned as toproduce in the circuit, a self-induction very large as compared whereby said secondary circuit may beelectrically tuned in resonance with said electromotive force and independent y of the rest of the system.

4.. The combination in 'a telegra hic sy'seachincluding a primary coil, a self-induccuits containing a secondary coil (in inductive proximity to one of said primary coils) a self-induction coil, and a capacity and atelc graphic receiving apparatus, means ofimposing two periodic electromotive forces upon said line, and telegraphic transmitting apparatus. arranged to vary said electromotive. forceszthe said parts bein constructed and combined so that each ranch circuit is tuned in a pr'oximate electrical resonance, and the in need secondary ircuit thereof'in electrical resonance with on of'said imposed electromotive forces.

5. In an electrical system the combination of a common conductor, means for, throwingseveral electromotive forces at different fre uencies onto the common conductor t ough transformers having cores which form closed magnetic circuits and having large magnetic leakage, selective parts receiving energy from the common conductor, and means for tuning each selective part to rethrown upon the commonconductor,. sub stantially as described.

6. The combination ina telegraphic sys cuits each including a primary coil, a self-inf structed and combined so that." each branch THOMAS EWING, Jr.-, SAMUEL W. BALOH.

'eriodic v temof a line conductor, two branc circuits tion coil and a capacity, two secondary cir-.

spond to one of the electromotive forces ectromotive forces upon said conductor, and telegraphic transmitting apparatus arranged to vary said e1ec tromotive forces; the said parts being con-' circuit is. tuned in aproximate electrical with the whole self-induction of the circuit; I

tem of a common conductor, two branch cirduction coil and a capacity, two secondary 

